In continuous ink jet printing, electrically conductive ink is supplied under pressure to a manifold region that distributes the ink to a plurality of orifices, typically arranged in a linear array(s). The ink discharges from the orifices and filaments which break into droplet streams. Individual droplets in the streams are selectively charged in the region of the break-off from filaments, and charged drops are deflected by electrostatic forces from their original trajectories. The deflected drops may be caught and recirculated and the undeflected drops allowed to proceed to a print receiving medium.
To selectively apply charge to the ink droplets, it is necessary to accurately control the locations that the ink droplets break-off from the filaments. Drop break-off can be controlled by applying a stimulating energy of predetermined frequency and amplitude to the ink filaments. Such stimulation controls not only the break-off point, but also the drop size and spacing as well. U.S. Pat. No. 4,999,647 issued Mar. 12, 1991 to Wood et al discloses an ink jet print head wherein stimulation is achieved simultaneously in a long row (4 inches) of ink jets. The stimulator disclosed by Wood et al employs a long rectangular body of high acoustic Q material such as stainless steel. A plurality of slots are formed in the body to discourage vibration in the longitudinal mode. A plurality of elongated piezoelectric strips are affixed to body in pairs on opposing surfaces between the slots. The piezoelectric strips are driven synchronously to excite the stimulator in a direction parallel with the ink jets. The strips of piezoelectric material are adhered to the sides of the stainless steel block with a thin layer of epoxy having a high modulus of elasticity. Unfortunately, it has been found that after many hours of operation, such epoxy bonds have begun to fail, resulting in a failure of stimulation in the print head.